I was just thinking about the general concept of yours which is using no onboard propellant, using some form of high density energy source on board or beamed, and using electromagnetically accelerated plasma to generate thrust and also reduce drag at the same time.

I was thinking what if you could do away with the rail system, and simply design a two phase system.

At low speeds you breathe atmosphere, ionise it internally, accelerate it out the back, then when you get to high speeds you switch to your concept of generating a supercavity externally and using the plasma outside the craft to accelerate.

For the first stage you might only need to ionise a certain percentage to heat the whole volume to high enough temperatures/pressure to produce thrust.

Also as speed increases you would pump more and more energy outside the craft to ionise and repel the atmosphere to create the supercavity.

At low density atmospheres you could potentially not only create plasma cavities to reduce drag, but you could also use the same system to increase drag and deccelerate by ionising large volumes of thin atmosphere and thrusting against the plasma flow with your magnetic fields.

With a sufficient energy source, we could orbit and deorbit large masses not just here on Earth but anywhere where there is an atmosphere, and we could also create atmospheric cruisers in the atmospheres of jovian planets.

All we need is power generation small enough to fit in a craft probably on the scale of an A380 with gigawatts of output, and an agile system to breathe, ionise and expel atmospheres of various composition, and ability to manipulate ionised atmospheres outside the craft as well.

Another spin off from this kind of plasma physics could be craft that can fly through or even stay for prolonged period in the upper atmosphere of the sun. Of course for that we would need radiation shielding technologies we have no clue about at this stage, but one can dream. Imagine flying in very tight orbits around the sun, somewhere in it's upper atmosphere, one could reach breakneck speeds on the order of hundreds of kilometers/s, and depending on trajectories this could be used for fast missions to any of our gas giants where one could use the same system to deccelerate in their atmosphere.

So you could launch from Earth, loose as much of your orbital momentum relative to the sun in our upper atmosphere by accelerating in the right direction relative to Earth's orbit, fall in towards the sun, then scrape its upper atmosphere and accelerate to many times solar escape velocity, then when you get to Neptune, you use it's atmosphere to deccelerate and enter orbit.

Possibly the gforces and radiation environments of such a mission wouldn't be too healthy for a living organism, but we could use this for "quick" movement of large amounts of material across the whole solar system. Also if we lose some into interplanetary space due to miscalculations or malfunction, there is no life lost.

So I think /with my extremely naive understanding of the physics involved/ your Zeropto concept has a lot of potential. A lot more than just getting stuff into Earth orbit without using any on board reaction mass.

Heck I just realised, one could use the same system to send back stuff from jovian planets. You use a gas giant's upper atmosphere to accelerate yourself into an orbit that falls towards the sun. Fall in scrape the upper atmosphere of the sun, but use it to reduce your orbital energy, then when you get to your target inner planet use their atmosphere to enter orbit around them.

The funny thing is that when you are close to the sun, you probably wouldn't need any on board energy source as long as you can use the irradiated energy to drive your plasma drive. Also if you can pump said irradiated energy into a plasma plume fast enought, it could double as your cooling system which means you don't have to worry about the thousands of kelvins around you. And probably you could use strong magnetic fields to shield against the high energy protons and electrons whizzing about leaving only gamma radiation and neutrons to deal with.

So really the Zeropto concept isn't merely a means to access LEO, it could be the means to access the whole solar system through advanced plasma physics and utilising high density power sources. It would mean no need to carry reaction mass anywhere, all you need is a dense energy source, smartly calculated trajectories, and know how of generating and handling strong magnetic fields and plasmas. /which interestingly is what we need for fusion power as well.../

So really the Zeropto concept isn't merely a means to access LEO, it could be the means to access the whole solar system through advanced plasma physics and utilising high density power sources. It would mean no need to carry reaction mass anywhere...

You would still need a propulsion system for free space maneuvers, orbital adjustments, mid-course trajectory corrections, etc.

You can't get to Orbit without using Reaction Mass. While it's theoretically possible to give it all the velocity on the ground a la your Railgun concepts, I can't see how to make it safe for human cargo in an atmosphere. Otherwise, all the Atmosphere using concepts lose efficience with altitude until you approach the zero-point where drag cancels the thrust from the thin ambient pressure. otherwise, we could fly Helicopters, and Balloons to the Moon. At some point, you Have to throw mass out the back to go foreward until we discover some way physics doesn't work the way we have always observed it to.

_________________"You can't have everything, where would you put it?" -Steven Wright.